Enlarge direct channel test buffer size to fit very fast rate

Test buffer size was not enough for very fast rate (800Hz). This
CL increased the buffer size so it will not fail on correct
implementation.

Test: SensorDirectReportTest passes for Pixel 2016/2017 devices
Bug: 37955438
Change-Id: Id585f04fb68750e4794eb4c299d75cd2dcc22890
2 files changed